Medical breathing apparatus

ABSTRACT

A breathing apparatus of the kind having a water chamber in which a heating element is immersed, the temperature of said element being controlled so that air drawn over the heated water is maintained at or close to a required humidity and temperature at an outlet, the volume of the air passing through the apparatus being substantially greater than that required for breathing and being directed into a face mask connectable to the outlet which is formed with vents through which excess moist/heated air together with air exhaled by a user can pass to atmosphere, is characterized in that the casing for the apparatus is in two parts, comprising a base and a removable housing, in that the base accommodates a water tank, and has a column extending upwards therefrom which defines an air path from the water tank in that the face mask is connected to the upper, outlet end of the column, and in that the heating element is carried by and projects from said removable housing such that it is immersed into the water of said tank when said housing is fitted into position on said base.

This invention relates to breathing apparatus for medical purposes.

It is known that humid air at around 90% relative humidity and acritical temperature of 43° C., when breathed by a patient for period of15 to 20 minutes, is effective in rendering groups of viruses in theupper respiratory tract inactive, which results in the body being ableto counteract colds, allergies, etc. efficiently and thereby reducedramatically the patient's recovery time.

The Applicant's co-pending U.K. Patent Specification No. 2192136,describes apparatus which incorporates an efficient temperature controlarrangement by which air drawn through the apparatus is supplied to theuser at or close to the critical humidity and temperature requirements.This apparatus has proved particularly successful in clinical trialsconducted by the Medical Research Council.

The object of the present invention is to provide a development of theapparatus described in our said co-pending Patent Specification which,compared with the various embodiments described therein, has furthermainly constructional, advantages.

According to this invention breathing apparatus of the kind having awater chamber in which a heating element is immersed, the thetemperature of said element being controlled so that air drawn over theheated water is maintained at or close to a required humidity andtemperature at an outlet, the volume of the air passing through theapparatus being substantially greater than that required for breathingand being directed into a face mask connectable to the outlet which isformed with vents through which excess moist/heated air together withair exhaled by the user can pass to atmosphere, is characterised in thatthe casing for the apparatus is in two parts, comprising a base and aremovable housing, in that the base accommodates a water tank and has acolumn extending upwards therefrom which defines an air path from thewater tank, in that the face mask is connected to the upper, outlet endof the column, and in that the heating element is carried by andprojects from said removable housing such that it is immersed into thewater of said tank when said housing is fitted into position on saidbase.

Preferably, the heating element is of the PTC (Positive TemperatureCo-efficient) type and is surrounded by a shroud, which may bedetachable, and which generally encloses said element, but providesopenings near the top of the shroud, the arrangemen being such that,when the apparatus is not in use the heating element cannot be touchedif the removable housing is removed, and when the apparatus is in usewater at the required temperature tends to be concentrated within theshroud and across the water surface, thereby providing a reduced thermalmass and a consequent improvement in temperature control.

The base and removable housing may be so shaped that, when fittedtogether, they provide a casing which tapers progressively to a smalldimension in plan from its lower to its upper end, thereby providingstability to the apparatus in use, in which case a frontal part of theapparatus projects upwardly from the base and is inclined to thevertical away from the user, said frontal part preferably comprisesfront and side walls which are generally of U-cross-section, and theside walls thereof co-operate when fitted with a similarly inclinedfront wall of said removable housing to define said column. Theremovable housing may conveniently accommodate all theelectrical/electronic components for the apparatus, which includes a fanand fan motor, said heating element, and a circuit arrangement therefor.The circuit arrangement may include provision for temperature controlincluding a temperature sensor for monitoring the temperature of themoist/heated air being inhaled, which is fitted in the removable housingso as to project into said column at or close to its outlet.

Conveniently, the water tank is removable from the base for easy fillingand cleaning.

In order that the invention may be readily understood, one embodiment ofbreathing apparatus in accordance therewith will now be described, byway of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of the apparatus,

FIG. 2 is a cross-sectional side view, on the line II--II of FIG. 1, and

FIG. 3 is a section on the line III--III of FIG. 2.

Referring to FIG. 1, it will be seen that the casing 1 is generally intwo parts consisting of a base 2 and a removable housing 3, the splitline being along the thickened line X--X (see also the chain dottedoutline of the housing 3 in FIG. 2). The front wall of the base (i.e.the wall facing the user) includes a column 4 which projects upwardly,but is inclined to the vertical away from the user. The upper end of thecolumn supports a face mask 5 via pivoted mountings 6, said face maskbeing provided with a series of slit openings 7, as described in oursaid co-pending Patent Specifiction No. 2192136.

Referring to FIG. 2, the base 2 has a continuous horizontal ledge 8extending around its front and side walls (see also FIG. 3) whichsupport an open water tank 9, via a flange 10 extending around the topof said tank. The inclined column 4 is generally of U-cross section andthe side walls 11 thereof (see also FIG. 1) co-operate (when fitted)with a similarly inclined front wall 12 of the removable housing 3 todefine a path, denoted by arrows 13, above the tank 9, for the flow (inuse) of moitst/heated air passed across the surface of water 14contained in the tank, to the face mask 5.

The removable housing 3 accommodates all the electrical/electoniccomponents for the apparatus, which are fed from a suitable power supplyvia an electric cable 17, (see FIG. 1). The components include a fan 18,which is rotatable within a volute casing 19 mounted on one (rearwardfacing) face of a support wall 20 extending vertically within thehousing 3, a fan motor 21 supported on the other face of the wall 20which is coupled to the fan via a drive shaft 22 extending through anopening in said wall, a PTC heating element 23, and, in this embodiment,a temperature control circuit board 24, and a temperature sensor 25. Thecircuit board 24 is also supported on said other face of the wall 20 andprovides a control arrangement, which is designed:

(i) to provide a power supply to the PTC heating element 23, whichprojects from the lower wall of the housing 3 so that (with the housingfitted), it is immersed in the water of the tank 9,

(ii) to provide a regulated power supply to the motor 21 so that the fan20 passes air drawn via slit openings 26 in the rear wall 15 of thehousing 3 across the water in the tank 9 to the face mask 5 via air path13 in a volume which (as described in our co-pending PatentSpecification No. 2192136) is greater than that required for inhaling,

(iii) to monitor the temperature of the air being breathed by the uservia the sensor 25, which comprises a probe mounted on the wall 12 of thehousing 3 so as to project into the air flow path 13 close to its upperoutlet end, and

(iv) to control the speed of the fan 18 to adjust the temperature of theair at the sensor probe position, as appropriate, to maintain thecritical temperature.

As mentioned hereinbefore, the control arrangement would also include atimer and/or alarm circuit to warn, and preferably switch-off theapparatus automatically, after a pre-set time period, e.g. 15 or 20minutes. Also, the circuit includes an indicator light 30 to show whenthe power is on and which is preferably arranged to flash when theapparatus is initially switched on until a stable working condition isreached.

The PTC heating element 23 is provided with a detachable shroud 27,which generally encloses said element, but provides openings 28 near thetop of the shroud (see FIGS. 1 and 2) of a suitable plastic materialwhich can withstand the temperature conditions, e.g. The shroud ensuresthat the user cannot directly touch the PTC element when the housing 3is removed from the base 2, thereby ensuring safety from burns. However,it is has been found that temperature control of the air passing to theface mask 5 is effected more efficiently with such a shroud fitted,probably in view of the fact that the water in the tank 9 below thewater surface is at a significantly lower temperature, due to theinsulating effect of the plastic shroud. This leads to water at therequired temperature being concentrated within the shroud and across thewater surface, thereby providing a reduced thermal mass.

Tests have shown that, in use, due to the inherent temperature stabilityof the PTC element and the further stability provided by the surroundingshroud, it is not essential to provide control means, including thesensor 25, to monitor and adjust the temperature of the air beinginhaled, thus enabling significant cost savings to be achieved.

I claim:
 1. A breathing apparatus of the kind having a water chamber inwhich a heating element is immersed in water, the temperature of thewater being controlled by the heating element so that air drawn over theheated water is maintained at an outlet of the apparatus at or close toa desired humidity and temperature, the volume of the air passingthrough the apparatus being substantially greater than that required forbreathing and being directed into a face mask, connected to the outlet,which is formed with vents through which excess moist heated airtogether with air exhaled by the user can pass to atmosphere,wherein anexterior casing of the apparatus is formed from a base and a matingremovable housing carrying electrical components including the heatingelement, the base comprises a water tank and at least a substantialportion of a duct extending therefrom which defines an air path for themoist heated air to travel from the water tank to the face maskconnected to a distal end of the duct, the heating element being carriedby the removable housing so that, once the removable housing is matinglyengaged with the base, the heating element is at least partly immersedin the water, when water is contained in the water tank, and the base,the at least substantial portion of the duct and the face mask remainingconnected to one another as a single unit upon disengagment of theremovable housing from the base.
 2. An apparatus according to claim 1,wherein the electronic components include a fan, a fan motor and acircuit means for powering and controlling the fan, the fan motor andthe heating element.
 3. An apparatus according to claim 2, wherein thecircuit means is provided with means of supplying power to the heatingelement only when the heating element is immersed in water contained bythe water tank.
 4. An apparatus according to claim 2, wherein thecircuit means further includes a temperature sensor which projects intothe column adjacent the outlet thereof and, during use, the temperaturesensor monitors the temperature of the moist heated air as it flowsthrough the column and provides an input to the circuit means which isused to control the electronic components.
 5. An apparatus according toclaim 2, wherein the circuit means is provided with means for providinga warning to a user after the user has used the apparatus for apredetermined period of time.
 6. An apparatus according claim 2, whereinthe circuit means further includes means for indicating to a user once astable state working condition of the apparatus has been achieved.